Log, Sep 6, 2002

33 people. What a joy it is to be able to write a log entry that isn't full of complaints about grismal weather. The night was quite good - probably a full 7 or so on the totally subjective FDO scale where 0 is fog to thick to see the heavy rain clouds obscuring a full Moon and 10 is moonless dark skies with transparency approaching meta physical perfection. Anything above a 5 is just fine. There were occasional clouds and by the wee hours, everything was damp and getting a bit chilly (upper 50s). However this night easily surpassed any night this summer - which admittedly wasn't much of a barrier to hurdle.

I had sent out a message earlier in the day alerting folks to the glare of two large lights left on since Rhythm and Roots. I've been in touch with various folks and have received promises that the lights will be turned off by next week. Yours truly has his fingers crossed and hoping. We had half a dozen astronomers set up in the alley way next to the Observatory yard but Satish Nagarajan took my suggestion and moved to a darker parking lot about a quarter mile farther down Park Lane to pursue photography free of the huge area lamps and car lights. It worked out pretty well.

The early visitors asked what planets would be up. Since the outer three planets are rarely interesting and barely show a disk, this seem to leave only Venus, but we stayed late enough to view Saturn and even Jupiter. Saturn was quite good but nothing like the nights when we could make out Enke's division. The Cassini Division was easy and markings were clear on the surface. Moons abounded with two moons just outside the ring - or so we thought. Turns out, it wasn't two moons but Mimas and a very faint background star. Had we watched long enough, we would have seem the background stars move the wrong way for one of Saturn's family. Jupiter was too close to the horizon to be anything worth noting.

Late in the night, Ernie Evans ran in excitedly and asked if we had seen Mira. Steve and I were obviously dull by this time because neither one of us had "seen her". Duhhh. Ernie was justifiably excited because Mira a.k.a Omicron Ceti was putting on a show. Mira (Latin for The Wonderful) is a pulsating Red Giant very close in astronomical terms to Earth. What is so amazing about Mira is the vast range of brightnesses its spans. At its brightest it is brighter than some of the stars in the big dipper but when it is at its dimmest it cannot be seen by either the naked eye or even through most binoculars. Currently Mira is reaching a peek in its cycle, giving the Whale (Cetus) an unusual extra bright star on its neck. Judging it against a neighboring star of known brightest, Mira is within a factor of two of its brightest, more than seven magnitudes more than its dimmest.

Mira is a large M6 super giant, a class of stars very close to the end of their life. It is ejecting large amounts of gas into clouds which sometimes obscure the star near its maximum causing some brightness peaks to be lower than normal. It is about 100 light years away, and ranges from near the second magnitude to dimmer than the tenth magnitude. It won't stay bright long. Most of the time Mira is an obscure star on a cycle of 322 days.

We saw a lot of crowd pleasers tonight, Venus, the Triffid, the Lagoon M54 (the escapee from the Sagittarius Galaxy which is running into the Milky Way Galaxy). We looked at double stars, nebulae and globular clusters. None of the ones we ran through were new.

We had lots of bright kids who knew lots about astronomy. I always like it when I mention clouds of gasses near a star and kids know that such masses are called nebulae. It was interesting to talk to kids about why the Milky Way looks like a big ring around the Earth with sections which wander off from the main band. The kids were sharp enough to understand that a spiral nebula see from inside would look just like what we were seeing.

I hope that tonight is the beginning of a chain of wonderful Friday nights this fall while it is still warm enough to be enjoyed. I look forward to see you folks at FDO on the next clear Friday evening.

-Les Coleman

Leslie Coleman
Leslie Coleman
Entry Date:
Sep 6, 2002
Published Under:
Leslie Coleman's Log
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